Conical flame waste gas combustion reactor

ABSTRACT

A reactor is provided which produces a hollow cone flame jet. The reactor is formed from a plurality of concentric casings, the inner casing defining a combustion chamber having a converging-diverging nozzle. A primary air chamber is axially positioned within the combustion chamber and has a second end having a substantially divergent conical shape.

BACKGROUND OF THE INVENTION

[0001] This invention relates to fuel burners such as are used in industrial furnaces. More particularly, the present invention relates to fuel reactors that may be used to burn polluted waste gases in a controlled combustion process.

[0002] Over the past several years it has proven difficult to design and build efficient furnaces because efficient burners may not be available. Exasperating the efficiency problem are the constant influx of new environmental regulations requiring the effective control of combustion pollutants such as nitrogen oxidants (NO_(x),) which in turn produce photochemical oxidants. The furnace design typically cannot control the emission of pollutants, therefore the burner must be designed to control the pollutants.

[0003] A high flame temperature in the burner creates the optimum condition of the atomic nitrogen in the combustion air to combine with the oxygen. Once NO is formed, the poisonous NO₂ is unavoidable.

[0004] One method which has been used to try to eliminate the formation of NO_(x), is to maintain a lower flame temperature. However, in most cases the methods which have been developed cause inefficiencies and incomplete combustion, generating carbon monoxide, soot deposits in the flue, and discharge of particulates into the atmosphere.

[0005] In addition, it is desirable in many applications to incinerate waste gases while maintaining low emissions of NO_(x). Waste gases may be a resultant by-product of chemical processes, refinery gas, pyrolysis, or incineration gas products or producer gas such as produced from coal gasification (e.g. SASOL gas). These gases usually have a medium or low heating value, so there is a need to provide a reactor with the capability of supplementing the waste gas with a clean gas.

[0006] Another problem frequently associated with conventional fuel burners is the lack of control over the momentum of the flame. Many burners provide very little control over the direction and amplitude of the flame, which may make it difficult to design an efficient furnace.

[0007] The present invention is directed toward overcoming, or at least reducing the effects of, one or more of the problems set forth above.

SUMMARY OF THE INVENTION

[0008] In accordance with one aspect of the invention there is provided a reactor including an outer casing with first and second ends, an inner casing with first and second ends, an annulus formed between the outer and inner casings, a reaction chamber, and an air inlet assembly with first and second ends. The air inlet assembly is substantially concentric with the inner and outer casings and a back plate connects the first ends of each of the inner casing, the outer casing, and the air inlet assembly. The second end of the air inlet assembly is substantially conical.

[0009] In some embodiments there is included an annulus divider forming an upper annulus and a lower annulus. The upper annulus may be a waste gas header and the lower annulus may be a secondary air header.

[0010] In some embodiments the air inlet assembly further includes an inner pipe with first and second ends and an outer pipe. The second end of the inner pipe may include a ring plate and an air passageway is defined by an annulus between the inner and outer pipes of the air inlet assembly. The air inlet assembly may include a plurality of air inlet orifices in the outer pipe facilitating fluid communication between the air inlet assembly and the reaction chamber.

[0011] In some embodiments the plurality of air inlet orifices are angled toward the second end of the air inlet assembly, for example the orifices may be angled at approximately 45° with respect to the outer pipe.

[0012] In some embodiments a plurality of orifices in the inner casing facilitate fluid communication between the reaction chamber and the annulus between the inner and outer casings. The plurality of orifices in the inner casing may be angled toward the second end of the inner casing, for example the plurality of orifices may be angled at approximately 45° with respect to the inner casing.

[0013] In some embodiments there is a clean gas header adjacent the first end of the inner casing. The clean gas header is defined by the back plate, the inner casing, the air inlet assembly, and a second plate. The second plate includes at least one orifice therein. The at least one orifice in the second plate may be centrally located between the inner casing and air inlet assembly. Preferably, there are a plurality of orifices spaced around the plate.

[0014] In some embodiments the inner casing further includes a converging-diverging nozzle, and the combination of the converging-diverging nozzle with the substantially conical-shaped second end of the air inlet assembly provide a hollow cone resultant flame jet.

[0015] In one aspect of the invention there is provided a reactor including a plurality of concentric casings defining a plurality of concentric chambers. The concentric chambers include a combustion chamber defined by concentric casings and a back wall, a primary air chamber axially positioned within the combustion chamber with the primary air chamber including a plurality of orifices facilitating communication between the primary air chamber and the combustion chamber, a secondary air chamber surrounding a first portion of the combustion chamber, the secondary air chamber including a plurality of orifices facilitating communication between the secondary air chamber and the combustion chamber, a waste gas chamber surrounding a second portion of the combustion chamber, the waste gas chamber including a plurality of orifices facilitating communication between the waste gas chamber and the combustion chamber, and a clean gas chamber adjacent to the first portion of combustion chamber, the clean gas chamber including at least one orifice facilitating communication between the clean gas chamber and the combustion chamber.

[0016] In some embodiments the clean gas chamber is defined by the concentric casings, the combustion chamber back wall, and a back plate. The primary air chamber may include an inner casing and an outer casing, each with first and second ends, where the second end of the outer casing is substantially conical. The second end of the inner casing may include a ring plate. An annulus between the inner and outer casing defines a primary air passageway.

[0017] In some embodiments the second portion of the combustion chamber comprises a converging-diverging nozzle. The combination of the converging-diverging nozzle and the substantially conical-shaped air inlet assembly provide a hollow cone resultant flame jet.

[0018] In some embodiments the at least one gas chamber orifice is located along the centerline of the combustion chamber.

[0019] In some embodiments the orifices of the primary air chamber, secondary air chamber, and waste gas chamber are angled in a downstream direction.

[0020] In another aspect of the invention there is disclosed a method of combusting waste gases including the steps of introducing a waste gas into a reactor, combusting the waste gas in the reactor with air and clean gas, and directing the resultant flame to form a hollow conical jet to facilitate fast cooling.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The foregoing and other features and aspects of the invention will become further apparent upon reading the following detailed description and upon reference to the drawings in which:

[0022]FIG. 1 is a cross-sectional view of one embodiment of a reactor in accordance with the present invention.

[0023]FIG. 2 is a partial top view of the embodiment shown in FIG. 1.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0024] Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, that will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

[0025] Turning now to the Figures, and in particular FIGS. 1-2, one embodiment of reactor 2 in accordance with the present invention is shown. Reactor 2 includes an outer casing 4 and an inner casing 6. Inner casing 6 and outer casing 4 may be made of a single piece as shown or they may be separate pieces subsequently attached. Inner casing 6 is substantially concentric with outer casing 4, although the shapes of each may be somewhat different from one another as shown in FIG. 1. Inner casing 6 and outer casing 4 are arranged such that they are substantially parallel at first end 26 but intersect at second end 28. A back plate 24 closes the gap between inner casing 6 and outer casing 4 at first end 26. Outer casing 4 includes a first cylindrical portion 30, a second cylindrical portion of reduced diameter 32, and a converging conical portion 34 connecting the two cylindrical portions. Inner casing 6 includes a cylindrical portion 36, a converging conical portion 38, and a diverging conical portion 40.

[0026] An annulus 8 is created between the inner and outer casings. Annulus 8 is divided into a lower annulus 10 and an upper annulus 12 by an annulus divider 14. Upper annulus 12 forms a chamber, for example a waste gas header 16. Waste gas header 16 is bounded by inner casing 6, outer casing 4, annulus divider 14, and back plate 24. Waste gas header 16 contains a waste gas that may be a resultant by-product of a chemical process, a refinery gas, pyrolysis or incineration gas products, producer gases such as the SASOL gases produced by coal gasification, or other waste gases having a relatively low or medium heating value. A waste gas flanged nozzle 18 is disposed in outer casing 4 adjacent upper annulus 12 to facilitate the introduction of waste gases into waste gas header 16.

[0027] Lower annulus 10 forms a second chamber, for example secondary air chamber 20. Secondary air chamber 20 is bounded by inner casing 6, outer casing 4, and annulus divider 14. A secondary air flanged nozzle 22 facilitates the introduction of air into secondary air chamber 20.

[0028] A third chamber, for example clean gas header 42, is disposed concentric with inner casing 6 at first end 26. Reactor 2 advantageously includes clean gas header 42 to provide the capability of producing a sufficient level of kinetic energy and temperature needed for dissociation of the waste gases that are comprised of large hydrocarbon molecules. Clean gas header 42 is generally cylindrical and is bounded by inner casing 6, back plate 24, an orifice plate 44, and an outer pipe 46. Outer pipe 46 is a component of an air inlet assembly 48, which is discussed below. The clean gas contained by clean header may be natural gas, methane, or any other gas with a high heating value. An entry port 50 supplies clean gas to clean gas header 42. Clean gas header 42 includes a plurality of orifices, for example clean gas orifices 52 spaced substantially equidistant from one another in the circular pattern shown in FIG. 2. Clean gas orifices 52 are arranged approximately half-way in between inner casing 6 and outer pipe 46 such that they align with a centerline 54 of a reaction chamber, for example combustion chamber 56.

[0029] Combustion chamber 56 is immediately interior to inner casing 6 and orifice plate 44. Clean gas orifices 52 are substantially perpendicular to orifice plate 44 along centerline 54 of combustion chamber 56 to facilitate introduction of clean gas into the combustion chamber.

[0030] Primary air inlet assembly 48 is axially positioned substantially in the center of combustion chamber 56. Primary air inlet assembly 48 includes outer pipe 46 and an inner pipe 62. Both outer pipe 46 and inner pipe 62 extend through clean gas header 42 at a first end 66 and into combustion chamber 56. Outer pipe 46 includes a cylindrical portion 64 and a substantially conical portion 68. Outer pipe 56 is closed at both first end 66 and second end 70 by end plates 69 and 72, respectively. Inner pipe 62 is open at both ends 66 and 70. A primary air passageway is thus created through the interior of inner pipe 62 and continuing through the annulus between inner pipe 62 and outer pipe 46. Inner pipe 46 may advantageously include a ring plate 74 directing primary air toward the edges of conical portion 68 of outer pipe 46 to facilitate cooling of outer pipe 46 beginning with second end 70 at the largest diameter of conical portion 68.

[0031] Each of air inlet assembly 48, waste gas header 16, and secondary air header 20 include a plurality of orifices facilitating introduction of gases from each into combustion chamber 56. Waste gas orifices 58 are arranged at an angle with respect to a line normal to inner casing 6 to aim the waste gases toward an exit nozzle 60. Similarly, secondary air header 20 includes secondary air orifices 76 arranged at an angle with respect to a line normal to inner casing 6 for aiming the secondary air toward exit nozzle 60. Opposite waste gas orifices 58 and secondary air orifices 76 are a plurality of primary air orifices 78. Primary air orifices 78 are arranged at an angle with respect to a line normal to outer pipe 46 for directing primary air toward exit nozzle 60. In the embodiment shown in the FIG. 1, each of primary orifices 78 advantageously has an associated opposite orifice at approximately the same elevation comprised of either waste gas orifices 58 or secondary air orifices 76. The association of orifices at approximately the same elevation facilitates uniform flow distribution and thus combustion control in combustion chamber 56. However, it will be understood by one of skill in the art with the benefit of this disclosure that in some embodiments (not shown) there may be some orifices in the primary air assembly, waste gas header, or secondary air header that are not associated with an opposite orifice. In the preferred embodiment, all of the orifices are substantially equally spaced around either inner casing 6 (with respect to orifices 58 and 76) or outer pipe 46 (with respect to orifices 78). The number of orifices and the impinging angles are functions of the capacity of the reactor, the heating value and composition of the waste gases. In the embodiment shown, the orifice angles for orifices 58, 76, and 78 are approximately 45 degrees. However, any angle between approximately 15 and 80 degrees may be used. It is within the ability of the skilled artisan in the relevant art, with the benefit of this disclosure, to determine an optimum angle for the orifices. The diameter of each orifice and the number of stages to be used are also functions of the heating value and composition of the waste gases. A stage is the cross section through the impact points of the primary jets of air, waste gas, and clean gas. In the exemplary embodiment shown as FIG. 1, there are five stages, but it will be understood that the number of stages can vary as the application requires. It is also within the ability of the skilled artisan with the benefit of this disclosure to determine the optimum diameter for the orifices and the number of stages for a particular reactor application.

[0032] As combustion of clean gas, waste gas, and air occurs, the gases flow through combustion chamber 56 toward exit nozzle 60. The gases traverse the converging portion of inner casing 6 and proceed through exit nozzle 60 which is defined by conical portion 68 of outer pipe 46 and diverging portion 40 of inner casing 6. The resultant flame jet 80 through exit nozzle 60 is a substantially hollow cone of high speed. Thermal NO_(x) formation is inhibited by a low chamber temperature and fuel NO_(x) is dissociated kinetically via molecular impacts and thermal stress (fast cooling). The substantially hollow conical flame jet 80 is thus advantageously useful in boiler and process heater applications as conical flame jet 80 radiates heat (shown as arrows 82) to the wall (not shown) to which reactor 2 is mounted and where there might exist heat transfer tubes (not shown) for the process.

[0033] In operation, clean gas enters port 50 and supplies clean gas to clean gas header 42. The clean gas in clean gas header 42 enters combustion chamber 56 through clean gas orifices 52. The clean gas can be treated as a collection of moving particles which create a first series of vectors as shown by arrow 90.

[0034] Primary air is introduced into reactor 2 through primary air passageway 84 where it is directed through inner pipe 62 to second end 86. Second end 86 is arranged in close proximity to end plate 72 of outer pipe 46. The close proximity of second end 86 to end plate 72 facilitates turbulent flow over the end plate. Turbulence increases the heat transfer rate from the plate to the incoming primary air, thus cooling the end plate which typically gains radiant heat when reactor 2 is used with a furnace or other type of closed heat processing chamber. Inner pipe 62 may also include ring plate 74 to direct the flow of primary air toward the largest diameter of conical portion 68 on outer pipe 46. Thus ring plate 74 facilitates cooling the entire conical portion 68 starting from the intersection between conical portion 68 and end plate 72.

[0035] Primary air continues through the annulus created between inner pipe 62 and outer pipe 46 before exiting primary air inlet assembly 48 through primary air orifices 78. As primary air exits primary air assembly 48, it enters combustion chamber 56. The primary air entering through primary air orifices 78 forms a series of vectors 92 which impinge vector 90.

[0036] Waste gas is directed into waste gas header 16 where it is directed into combustion chamber 56 through waste gas orifices 58. The waste gas passing through orifices 58 forms a series of vectors 94 which impinge vectors 90 and 92. The mixture of clean gas, air, and waste gas are ignited by a suitable pilot (not shown).

[0037] In a preferred embodiment, orifices 58 and 78 are sized and the air, and waste gas pressures are regulated such that the resultant vector formed by vectors 92 and 94 is in the same direction as vector 90. The annular area where vectors 90, 92, and 94 meet defines a first combustion zone. In the embodiment shown in FIG. 1, there are three such combustion zones employing waste gas, but any number of zones may be created.

[0038] Similarly, secondary air is directed into secondary air header 20 where it is directed into combustion chamber 56 through secondary air orifices 76. The secondary air passing through orifices 76 forms a series of vectors 98 that impinge vectors 100 and 102 (which are created by the resultant vectors above and primary air, respectively). The series of vectors 98, 100, and 102 create another combustion zone to incinerate any unburned hydrocarbons. FIG. 1 discloses two such combustion zones employing secondary air, however any number of the additional combustion zones may be formed.

[0039] All of the combustion gases continue through combustion chamber 56 and exit through exit nozzle 60. Exit nozzle 60 forms a high speed conical jet 80 as previously described. High speed includes speed in excess of 200 feet per second, for example the speed of the jet may be 550 feet per second in some applications. The high speed flame advantageously inhibits NO_(x) formation while burning low heating value waste gases.

[0040] As can be seen from the foregoing, the present invention provides a novel waste gas reactor which maintains a low flame temperature to avoid the formation of pollutants while achieving complete combustion through the use of multiple stage combustion. The invention provides for the use of a clean gas to promote the combustion of the waste gases. Additionally, the gas particles are directed to designated angles facilitating control of discharge jet velocity and therefore flame momentum.

[0041] While the present invention has been described with reference to the specific embodiments, it will be appreciated that the invention may be embodied in other specific forms without departing from its spirit and scope. For example, with some variations, reactor 2 can be adapted to burn liquid fuels. Accordingly, the described embodiment is to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. 

What is claimed is:
 1. A reactor comprising: an outer casing with first and second ends; an inner casing with first and second ends wherein the second end forms a converging-diverging nozzle; an annulus formed between the outer and inner casings; a reaction chamber formed within the inner casing; an air inlet assembly with first and second ends, wherein the air inlet assembly is substantially concentric with the inner and outer casings; wherein the second end of the air inlet assembly has a substantially divergent conical shape.
 2. The reactor of claim 1 further comprising an annulus divider forming an upper annulus and a lower annulus.
 3. The reactor of claim 2 wherein the upper annulus comprises a waste gas header.
 4. The reactor of claim 2 wherein the lower annulus comprises a secondary air header.
 5. The reactor of claim 1 wherein the air inlet assembly further comprises an inner pipe with first and second ends and an outer pipe.
 6. The reactor of claim 6 wherein the second end of the inner pipe comprises a ring plate positioned within the second end of the air inlet assembly.
 7. The reactor of claim 5 further comprising an air passageway defined by an annulus between the inner and outer pipes of the air inlet assembly.
 8. The reactor of claim 5 further comprising a plurality of air inlet orifices in the outer pipe facilitating fluid communication between the air inlet assembly and the reaction chamber.
 9. The reactor of claim 8 wherein the plurality of air inlet orifices are angled toward the second end of the air inlet assembly.
 10. The reactor of claim 9 wherein the plurality of air inlet orifices are angled at approximately 45° with respect to the axis of the outer pipe.
 11. The reactor of claim I further comprising a plurality of orifices in the inner casing facilitating fluid communication between the annulus between the inner and outer casings and the reaction chamber.
 12. The reactor of claim 11 wherein the plurality of orifices in the inner casing are angled toward the second end of the inner casing.
 13. The reactor of claim 12 wherein the plurality of orifices are angled at approximately 45° with respect to the axis of the inner casing.
 14. The reactor of claim 1 further comprising an orifice plate forming a clean gas header adjacent the first end of the inner casing.
 15. The reactor of claim 1 wherein the combination of the converging-diverging nozzle and the substantially conical-shaped second end of the air inlet assembly provide a hollow cone resultant flame jet.
 16. A reactor comprising a plurality of concentric casings defining a plurality of concentric chambers including: a combustion chamber defined by concentric casings and a back wall wherein the combustion chamber includes a converging-diverging nozzle; a primary air chamber axially positioned within the combustion chamber, the primary air chamber including a plurality of orifices facilitating communication between the primary air chamber and the combustion chamber and wherein a portion of the primary air chamber extends into the nozzle; a secondary air chamber surrounding a first portion of the combustion chamber, the secondary air chamber including a plurality of orifices facilitating communication between the secondary air chamber and the combustion chamber; a waste gas chamber surrounding a second portion of the combustion chamber, the waste gas chamber including a plurality of orifices facilitating communication between the waste gas chamber and the combustion chamber; and a clean gas chamber adjacent to the first portion of combustion chamber, the clean gas chamber including at least one orifice facilitating communication between the clean gas chamber and the combustion chamber.
 17. The reactor of claim 16 wherein the primary air chamber further comprises an inner pipe and an outer pipe, each with first and second ends, wherein the second end of the outer pipe has a substantially divergent conical shape.
 18. The reactor of claim 17 wherein the second end of the inner pipe further comprises a ring plate.
 19. The reactor of claim 17 wherein an annulus between the inner and outer pipes defines a primary air passageway.
 20. The reactor of claim 17 wherein the combination of the converging-diverging nozzle and the substantially conical-shaped air inlet assembly provide a hollow cone resultant flame jet. 